Dynamic desorption of macromolecules from solid surfaces by low-molecular-weight displacers

A novel dynamic approach to polymer desorption study has been tested. The adsorbent under study was packed into an HPLC-like adsorption-desorption column (ADC). Constant amount of polymer was dynamically preadsorbed within the ADC from an adsorption promoting liquid (adsorli) and desorbed subsequently by changing composition of a displacer consisting of an adsorli and a desorption promoting liquid (desorli). Polymer in the ADC effluent was detected with help of an evaporative light scattering detector using an appropriate calibration for each system. Dynamic integral desorption isotherms were obtained by plotting desorbed amount of polymer versus displacer composition. Both the attachment and detachment of polymer onto/from nonporous silica adsorbent surface were found to be very fast as far as the adsorbent surface was undersaturated. The courses of desorption isotherms were measured and compared for various systems, viz. polymer nature, polymer molar mass and molar mass distribution as well as adsorli and desorli nature. The effects of experimental conditions such as flow rate, temperature, amount of preadsorbed polymer and ADC size on the shapes of desorption isotherms were evaluated, as well. All above parameters influence the courses of desorption isotherms and it is shown that the described measurements can give valuable information on the desorption processes in the dynamic systems. The described dynamic desorption measurements are fast and the results obtained are repeatable. Moreover, both the sample and the sorbent consumption are low. (C) 2000 Elsevier Science B.V. All rights reserved.